Anharmonic lattice dynamics and superionic transition in AgCrSe2
- Duke Univ., Durham, NC (United States); Duke University
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Duke Univ., Durham, NC (United States)
Intrinsically low lattice thermal conductivity ( ) in superionic conductors is of great interest for energy conversion applications in thermoelectrics. Yet, the complex atomic dynamics leading to superionicity and ultralow thermal conductivity remain poorly understood. Here, we report a comprehensive study of the lattice dynamics and superionic diffusion in from energy- and momentum-resolved neutron and X-ray scattering techniques, combined with first-principles calculations. Our results settle unresolved questions about the lattice dynamics and thermal conduction mechanism in . We find that the heat-carrying long-wavelength transverse acoustic (TA) phonons coexist with the ultrafast diffusion of Ag ions in the superionic phase, while the short-wavelength nondispersive TA phonons break down. Strong scattering of phonon quasiparticles by anharmonicity and Ag disorder are the origin of intrinsically low . The breakdown of short-wavelength TA phonons is directly related to the Ag diffusion, with the vibrational spectral weight associated to Ag oscillations evolving into stochastic decaying fluctuations. Furthermore, the origin of fast ionic diffusion is shown to arise from extended flat basins in the energy landscape and collective hopping behavior facilitated by strong repulsion between Ag ions. These findings offer fundamental insights into the complex atomic dynamics of superionic conductors.
- Research Organization:
- Duke Univ., Durham, NC (United States); Argonne National Laboratory (ANL), Argonne, IL (United States); Univ. of California, Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division
- Contributing Organization:
- Oak Ridge National Laboratory Spallation Neutron Source; National Energy Research Scientific Computing Center
- Grant/Contract Number:
- SC0019299; SC0016166; AC02-06CH11357; AC02-05CH11231
- OSTI ID:
- 1598277
- Alternate ID(s):
- OSTI ID: 1607011; OSTI ID: 1632173; OSTI ID: 1598367
- Journal Information:
- Proceedings of the National Academy of Sciences of the United States of America, Journal Name: Proceedings of the National Academy of Sciences of the United States of America Journal Issue: 8 Vol. 117; ISSN 0027-8424
- Publisher:
- National Academy of SciencesCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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